Glass compositions which combine good chemical durability with the capability of being formed at low temperatures, i.e., the compositions have low transition temperatures (Tg), are potentially useful for a host of applications including low temperature sealing glasses, matrices for glass-polymer alloys, and press molding optically finished lenses. To illustrate:
U.S. application Ser. No. 07/704,864, filed May 23, 1991 by George H. Beall, James E. Dickinson, Jr., and Robert M. Morena under the title ZINC PHOSPHATE LOW TEMPERATURE GLASSES and assigned to the same assignee as the present application, now U.S. Pat. No. 5,122,484 is directed with particularity to low melting, lead-free glass compositions suitable as sealing frits in television picture tube applications. Those glasses are essentially free of PbO and consist essentially, expressed in terms of weight percent on the oxide basis, of:
______________________________________ P.sub.2 O.sub.5 38-50 SnO.sub.2 0-10 Al.sub.2 O.sub.3 0-5 MoO.sub.3 0-10 ZnO 28-42 WO.sub.3 0-10 Li.sub.2 O 0.75-5 MoO.sub.3 + WO.sub.3 2-15 Na.sub.2 O 2-10 Cl 0-8 (analyzed) K.sub.2 O 2-10 SnO.sub.2 + MoO.sub.3 + 2-25 Li.sub.2 O + Na.sub.2 O + 5-25 WO.sub.3 + Cl K.sub.2 O ______________________________________
U.S. Pat. No. 5,043,369 (Bahn et al.) broadly discloses the production of melt blends or alloys composed of a glass and an organic polymer. The disclosed articles comprise a melt mixture of an inorganic glass and an organic polymer, the working temperature of the glass being compatible with that of the polymer. That patent referred to U.S. Pat. No. 4,920,081 (Beall et al.) and U.S. Pat. No. 4,940,677 (Beall et al.) as describing glass compositions having working temperatures and transition temperatures suitable for use in preparing melt blends or alloys.
U.S. Pat. No. 4,920,081 recites glass compositions consisting essentially, expressed in terms of mole percent on the oxide basis, of:
______________________________________ P.sub.2 O.sub.5 44-58 Li.sub.2 O 0-30 Al.sub.2 O.sub.3 0-7 Na.sub.2 O + Li.sub.2 O 10-45 B.sub.2 O.sub.3 0-10 Cu.sub.2 O 0-20 Al.sub.2 O.sub.3 + B.sub.2 O.sub.3 4-10 Li.sub.2 O + Cu.sub.2 O 10-30 Na.sub.2 O 10-30 ______________________________________
with, optionally, up to 8% total of at least one member of the group MgO, CaO, SrO, BaO, MnO, and ZnO, up to 8% ZrO.sub.2, up to 3% SiO.sub.2, and up to 5% F.
U.S. Pat. No. 4,940,677 reports glass compositions consisting essentially, expressed in terms of mole percent on the oxide basis, of 10-35% R.sub.2 O, wherein R.sub.2 O consists of at least two alkali metal oxides in the indicated proportions selected from the group 0-25% Li.sub.2 O, 0-25% Na.sub.2 O, and 0-25% K.sub.2 O, 23-55% ZnO, 28-40% P.sub.2 O.sub.5, and up to 35% total of the following optional ingredients in the indicated proportions selected from the group 0-6% Al.sub.2 O.sub.3, 0-8% B.sub.2 O.sub.3, 0-8% Al.sub.2 O.sub.3 +B.sub.2 O.sub.3, 0-15% Cu.sub.2 O, 0-5% F, 0-35% PbO, 0-35% SnO, 0-35% PbO+SnO, 0-5% ZrO.sub.2, 0-4% SiO.sub.2, and 0-15% MgO+CaO+-SrO+BaO+MnO, consisting of 0-10% MgO, 0-10% CaO, 0-10% SrO, 0-12% BaO, and 0-10% MnO.
U.S. Pat. No. 5,021,366 (Aitken) provides glass compositions which were designed specifically for use in press molding optically finished lenses, but which are also suitable for use in preparing melt blends of glass and organic polymer. That patent records glass compositions consisting essentially, expressed in terms of mole percent on the oxide basis, of:
______________________________________ Li.sub.2 O 5-10 Al.sub.2 O.sub.3 0-5 Na.sub.2 O 5-15 CeO.sub.2 0-2 K.sub.2 O 0-6 P.sub.2 O.sub.5 30-36 Li.sub.2 O + Na.sub.2 O + K.sub.2 O 15-25 SnO 0-20 ZnO 10-33 PbO 0-20 CaO + SrO + BaO 12-25 Sb.sub.2 O.sub.3 0-12 CaO 0-20 Bi.sub.2 O.sub.3 0-6 SrO 0-20 SnO + PbO + 0-20 BaO 0-20 Sb.sub.2 O.sub.3 + Bi.sub.2 O.sub.3 ______________________________________
The lenses molded from those compositions exhibited refractive indices of about 1.605 and linear coefficients of thermal expansion (25.degree.-300.degree. C.) between 145-170.times. 1O.sup.-7 /.degree.C.
U.S. application Ser. No. 07/696,173, filed May 6, 1991 by me under the title HIGH INDEX FLUORINE-FREE PHOSPHATE GLASSES and assigned,,to the same assignee as the present application, now U.S. Pat. No. 5,153,151 is likewise directed principally to glass compositions designed for use in press molding optically finished lenses, but wherein refractive indices between 1.65-1.8 can be obtained. The glasses, having compositions expressed below in terms of mole percent on the oxide basis, are also noted as being operable in preparing glass-plastic alloys.
______________________________________ P.sub.2 O.sub.5 24-36 Al.sub.2 O.sub.3 0-5 ZnO 0-45 SrO 0-20 Li.sub.2 O 0-15 BaO 0-20 Na.sub.2 O 0-20 CaO + SrO + BaO 0-25 K.sub.2 O 0-10 Sb.sub.2 O.sub.3 0-61 Ag.sub.2 O 0-25 Bi.sub.2 O.sub.3 0-10 Tl.sub.2 O 0-25 Sb.sub.2 O.sub.3 + Bi.sub.2 O.sub.3 0-61 Li.sub.2 O + Na.sub.2 O + 15-30 Sb.sub.2 O.sub.3 + Bi.sub.2 O.sub.3 7-76 K.sub.2 O + Ag.sub.2 O + Tl.sub.2 O Ag.sub.2 O + Tl.sub.2 O PbO 0-20 B.sub.2 O.sub.3 0-10 CuO 0-5 Al.sub.2 O.sub.3 + B.sub.2 O.sub.3 0-10 CaO 0-20 SnO 0-5 CeO.sub.2 0-2 ______________________________________
with the following provisos:
(1) in the absence of Sb.sub.2 O.sub.3 and/or Bi.sub.2 O.sub.3, the total Ag.sub.2 O and Tl.sub.2 O will range 11-25;
(2) in the absence of Ag.sub.2 O and/or Tl.sub.2 O, the total Sb.sub.2 O.sub.3 +Bi.sub.2 O.sub.3 will range 7-61;
(3) when present in the absence of Bi.sub.2 O.sub.3 and/or Ag.sub.2 O and/or Tl.sub.2 O, Sb.sub.2 O.sub.3 will range 10-61, and, when present in the absence of Sb.sub.2 O.sub.3 and/or Ag.sub.2 O and/or Tl.sub.2 O, Bi.sub.2 O.sub.3 will range 7-10;
(4) when present in the absence of Bi.sub.2 O.sub.3, Sb.sub.2 O.sub.3, and Tl.sub.2 O, Ag.sub.2 O will range 13-25; and
(5) when present in the absence of Ag.sub.2 O, Bi.sub.2 O.sub.3, and Sb.sub.2 O.sub.3, Tl.sub.2 O will range 11-25.
The glasses exhibited annealing points between 300.degree.-340.degree. C., linear coefficients of thermal expansion (25.degree.-300.degree. C.) between 135-180.times.10.sup.-7 /.degree.C., and weight losses after exposure to boiling water for six hours no greater than 0.33%.
Further laboratory research has led to the discovery of transparent glasses having compositions within closely-circumscribed limits which demonstrate very low annealing points, i.e., less than 325.degree. C. with some compositions having annealing points as low as about 290.degree. C., improved chemical durability and resistance to weathering, and indices of refraction between 1.57-1.66, which indices are compatible with certain transparent organic polymers, such as polycarbonate (n.sub.d =1.586), polysulfone (n.sub.d =1.633)and polyethersulfone (n.sub.d =1.650), thereby recommending their utility in preparing transparent glass-plastic melt blends and composites.